Suction press roll for papermaking

ABSTRACT

A SUCTION PRESS ROLL FOR PAPERMAKING MACHINES HAS A RIGID HOLLOW ROLL COVERED BY A RESILIENT MATERIAL WITH ALIGNED SUCTION HOLES EXTENDING THROUGH THE MATERIAL AND ROLL FOR DRAWING WATER FROM A WET WEB PASSING THEREOVER AND WHICH MATERIAL HAS A PLURALITY OF DRAIN CHANNELS IN THE PERIPHERY THEREOF CONNECTING EACH PAIR OF SAID HOLES AND EACH OF SAID CHANNELS IS OF GREATER DEPTH THAN WIDTH PROVIDING AT LEAST ONE FLEXIBLE PROJECTING LAND BETWEEN THE CHANNELS WHICH LAND OR LANDS FLEX WHEN PRESSED BY A PLAIN ROLL AND THE WET WEB THEREABOVE CLOSING ONE CHANNEL PUSHING WATER THEREFROM AND OPENING THE NEXT CHANNEL FACILITATING THE FLOW OF WATER THEREIN TO SAID HOLES.

Feb. 16, 1971 SHOGO KQBAYASHI 3,562,883

SUCTION PRESS ROLL FOR PAPERMAKING Filed June 26, 1968 3 Sheets-Sheet 1 FIG. I

[Li-U l l L l.

INVENTOR Sk /060 KoBAYASH/ & MWaZ/ZS Feb. 16, 1971 SHOGO KOBAYASHI 3,562,883

SUCTION PRESS ROLL FOR PAPERMAKING Filed June 26, 1968 3 Sheets-Sheet z FIG.3

FIG.5 F|G.6

INVENTOR SHOGO KOBAYASH/ ATTORNEYS Feb. 16, 1971 SHOGO KOBAYASHI 3,562,883

SUCTION PRESS ROLL FOR PAPERMAKING Filed June 26, 1968 3 Sheets-Sheet I Fl G.7 FIG.8

INVENTOR sHoco KGB/WASH! B5 fizit voizii United States Patent 3,562,883 SUCTION PRESS ROLL FOR PAPERMAKING Shogo Kobayashi, 227 Mitoshima, Fuji-shi, Shizuoka-ken, Japan Filed June 26, 1968, Ser. No. 740,159 Int. Cl. B2lh 8/02 U.S. Cl. 29-121 1 Claim ABSTRACT OF THE DISCLOSURE A suction press roll for papermarking machines has a rigid hollow roll covered by a resilient material with aligned suction holes extending through the material and roll for drawing water from a wet web passing thereover and which material has a plurality of drain channels in the periphery thereof connecting each pair of said holes and each of said channels is of greater depth than width providing at least one flexible projecting land between the channels which land or lands flex when pressed by a plain roll and the wet web thereabove closing one channel pushing water therefrom and opening the next channel facilitating the flow of water therein to said holes.

The present invention relates to a suction press roll to be used in the web-pressing stage and elsewhere in a papermaking machine for dewatering a web.

In a papermaking process, suction press rolls are used primarily in the pressing stage, where they play a very important role. If the wet web is sufficiently dewatered by the suction press rolls in the pressing stage, an important saving may be obtained in the subsequent drying stage. Specifically, it is said that a one-percent improvement in the rate of dewatering in the pressing stage is equivalent to a five-percent saving in the operating cost of the drying stage, that is, in steam consumption there.

Thus, the suction press rolls play a vital role in dewatering the wet web. Especially, in a latest machine with a high papermaking speed of 300 meters or more per minute, the efliciency of its suction press rolls has even greater influence on the performance of the machine.

Heretofore, the art concerning suction press rolls has involved the use of a press roll containing a number of suction holes each of which, as it approaches the nip with another roll, allows water from the pressed web to drain through the hole. Such suction press rolls, however, if used in a machine with a papermaking speed of 300 meters or more per minute, often fail to drain all water from the pressed web through their suction holes alone, with the result that a pool of free water occurring immediately before the nip tends to cause the wet web to be crushed. Moreover, a considerable pressure difference between holes and lands on the surface of the roll often creates shadow marks on the web. The art has endeavored to increase the draining capacity of the suction press roll by providing more holes in it for increasing the diameter of its holes. But there is a limit to what one can expect to achieve by these approaches. A roll with too many holes or with too large holes may become so infirm as to be deformed under pressure or shake during rotation. or may tend to leave shadow marks on the web due to the presence of suction holes. In addition, such a roll is often uneconomical as its manufacturing cost is high.

The art concerning suction press rolls has also involved a design in which the roll body is provided on the surface with a number of linear drain channels running side by side in the circumferential direction or with spiral drain channels, through which free water from the web is led over the roll surface to be let out. Neither of these approaches is quite satisfactory, however, as linear channels tend to leave shadow marks on the web whereas spiral Patented Feb. 16, 1971 ICC channels present too much resistance to water from the web to permit its eflicient draining. Therefore, designers in the past have been compelled to use a number of conventional suction press rolls in the drying stage for successive draining of water from the web. Accordingly, the machine has been more expensive and required more space for installation than it would have without such numerous rolls.

The present invention is a successful solution to these various problems presented by the conventional type of suction press rolls. The main object of the invention is to provide a suction press roll which can dewater a wet web more efliciently than the conventional suction press roll under the same pressing load.

The second object of the present invention is to provide a suction press roll which not merely has the abovedescribed feature and advantage of being more eflicient in dewatering the wet web than the conventional roll but also leaves no shadow marks on the web.

The third object of the present invention is to provide a suction press roll which, in addition to the foregoing, has the advantage of being economical in structural design, its structure being such that the above-mentioned advantages can be obtained with little additional effort needed in manufacturing the roll beyond what is normally required in making a conventional press roll.

The foregoing objects are achieved by the present invention in the following manner:

A suction press roll embodying the invention consists of a rigid cylinder surfaced around the circumference with an elastic material. Conventional in dimensions and structure, the roll now in question has a number of suction holes arranged at equal intervals along spirals running around the circumference of the roll over its entire effective pressing length, with a drain channel or channels connecting said drain holes along each spiral. Thus, each hole is equally spaced from the one immediately preceding it along the same spiral, whereas it is regularly deviated in the roughly circumferential direction from its counterpart in the immediately preceding spiral. Said drain channel or channels are narrower than the diameter of the suction holes they connect, and each spiral row of holes may be served either by a single channel or a plurality of channels.

A typical embodiment of the present invention and modifications thereof are described in the accompanying drawings in which:

FIGv 1 is a side view of a roll embodying the invention, partly showing its suction holes and drain channels in development and partly cut away;

FIG. 2 is a development showing the arrangement of suction holes in the same roll;

FIG. 3 is a magnified plan showing how the suction holes are connected by a drain channel in the same roll;

FIG. 4 is a section taken along the line II in FIG. 3;

FIG. 5 is a magnified section of a part of the same roll showing a drain channel closed at the top;

FIG. 6 is a vertical section of a part of the same roll taken along a drain channel and showing how a wet web is dewatered on the roll;

FIG. 7 is a magnified plan of a part of a modified embodiment of the present invention showing two parallel drain channels running through a suction hole;

FIG. 8 is a section taken along the line II-II in FIG. 7;

FIG. 9 is a section showing one of the two drain channels in FIG. 7 closed at the top;

FIG. 10 is a magnified plan of a part of another modified embodiment of the present invention showing three parallel drain channels running through a suction hole;

FIG. 11 is a section taken along the line III-III in FIG. 10; and

FIG. 12 is a section showing one of the three drain channels in FIG. 10 closed at the top.

These practical embodiments of the invention are described below in conjunction with the accompanying drawings:

Generally, a roll embodying the present invention is conventional in dimensions and structure, and consists of a metal cylinder 2 and a covering 3 of an elastic material like rubber wrapped around its circumference. The effective length of the roll 1 in the axial direction is indicated as L in FIG. 1, beyond which the roll is slightly beveled toward either end for an axial distance I. The cylinder 2 and the covering 3 are tightly covered at either end with a cap 4 or 4' and supported by a bearing 5 or 5, respectively. Suction holes 6 are arranged at equal intervals along each of a number of spirals running around the roll 1 over its entire effective pressing length L. If the spirals S are counterclockwise, as shown in FIG. 1, each suction hole on a spiral is deviated regularly downward from its counterpart in the preceding spiral, the deviation being large enough to keep the two suction holes from overlapping each other when viewed in perspective from the axial direction. This design feature is important for the purpose of preventing shadow marks on the web, as will be explained later in detail.

The above-described arrangement of the suction holes 6 and the oblique angle of the spirals S formed by them are shown in a more concrete form in FIG. 2, where it is seen that the circumference is divided into equal major parts a whereas the effective length L is divided into equal parts whose length a is about the same as a. Thus one obtains a roughly square figure, a by a, at each vertex of which a suction hole is located. The square a by a holds therein a large rhombus, b by b, which in its turn contains a number of smaller rhombuses, c by 0', each of which has a suction hole 6 at each of its vertexes, and has its roughly circumferential sides lying at an angle 0 to the circumference. This angle is the oblique angle of the spirals S.

The row of suction holes 6 along each spiral S is connected in the roughly circumferential direction by a drain channel 7, which should preferably follow the center line of the suction holes 6 in the roughly circumferential direction, although a little deviation of the drain channel from the center line may be tolerated.

The width of the drain channel 7 should be smaller than the diameter of the suction holes 6, or 0.5 mm. to 1 mm. in quantitative terms, and the depth of the drain channel 7 should be about three times its width. Being limited in width, and considerable in depth in comparison with the width, the drain channel 7, because of the elasticity of the covering 3, closes at the top under the roll pressure near the roll nip N, and the pressure exerted by by the closing tops causes water in the channel to be pushed out.

In the roll 1, as in any conventional suction press roll, there is a suction box 8 that sucks water from the suction holes at the roll nip N and in its neighborhood.

In FIG. 6, a suction press roll 1 embodying the present invention is set below a plain roll 9, between which a guide felt 10 carrying a wet web 11 is fed in. With ordinary pressure applied by the plain roll 9, the suction roll 1 turns in the arrow-marked direction. Approaching the roll nip N, the web 11 is pressed and dewatered through the guide felt 10. Part of the water from the web is removed directly through the suction holes 6 while water pressed in each land area (identified as a in FIG. 2) between suction holes in a spiral row flows into several drain channels 7. Passing through the nip, the channels 7 close their tops under the roll pressure, causing water in each channel to be pushed out forward and backward and removed through the suction holes 6 immediately before and behind. Also, water collecting before the nip flows into several drain channels 7, and as the channels 7 pass through the nip, a similar effect to that just described causes said water to be removed through the suction holes 6 immediately before and behind.

The conventional type of suction press roll, which contains many suction holes in it, often leaves shadow marks on a web as it is pressed because of a pressure difference between the holes under suction and the land areas under the atmospheric pressure. The greater the pressure difference, the more likely the web is to vget shadow marks.

A suction press roll embodying the present invention, on the other hand, has several drain channels 7 running in each land area. They lower the pressure there below the atmospheric pressure and reduce the pressure difference from the suction holes 6, thus eliminating the cause of shadow marks.

A modified embodiment of the present invention is illustrated in FIGS. 7 to 9. Whereas the embodiment just described has a single drain channel between suction holes 6 in each spiral row, the present modification has two parallel channels, 7a and 7b, there. The land 12 between the two channels, being more flexible than ordinary lands elsewhere, flexes either rightward or leftward under the roll pressure as it passes through the roll nip N, resulting, as shown in FIG. 9, for example, in closing the left-side channel 7a and causing water therein to be pushed out while opening the right-side channel 7b and facilitating the flow of water therein.

Another modification is illustrated in FIGS. 10 to 12, in which three parallel drain channels, 7c 7d and 7e, are shown between suction holes 6 in each spiral row. The lands 13 and 14 between the drain channels, being more flexible than ordinary lands elsewhere, flex either rightward or leftward under the roll pressure as they pass through the roll nip N, resulting, as shown in FIG. 12, for example, in closing the central drain channel 7d and causing water therein to be pushed out while opening the two sided rain channels 70 and 7e and facilitating the How of water therein.

Facilitating the flow of water across the lands (or, generally, the land areas) not merely helps prevent shadow marks by reducing the pressure difference between lands and suction holes, as pointed out above, but also facilitates the dewatering of the wet web.

From the above description, it will be understood that modifications using two, three or more parallel drain channels running through suction holes in each spiral row may be resorted to without departing from the spirit of the present invention.

As a practical way of machining drain channels connecting suction holes in the above-described fashion, one may either make suction holes first along a spiral path and then follow the same path in cutting a drain channel or channels, or cut a drain channel or channels first along a spiral path and then follow the same path in making suction holes. In either case, one can perform both machining operations by following the same path. This makes the machining much simpler and less costly.

From the above description, it may be understood that the invention effectively serves its intended purposes, that is, providing a suction press roll which is more efficient than the conventional type in dewatering a wet web, less liable to leave shadow marks on the web, more machinable, and more economical.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that the invention is not limited thereto but that other design modifications and variations may be resorted to without departing from the spirit of the invention.

I claim:

1. A suction press roll for papermaking machines comprising a rigid hollow cylinder, a covering of an elastic material encasing the periphery of said cylinder, said cylinder having spaced apart suction holes extending therethrough from the periphery to the interior of said cylinder with said holes positioned along spirals extending around the periphery and over the entire pressing length of said cylinder, said covering having holes therethrough from the periphery of said cover to the periphery of said cylinder and each of said covering holes being in alignment with one of said cylinder holes, said covering further having at least a pair of spaced apart drain channels provided in the periphery thereof connecting each pair of said covering holes and each drain channel being of greater depth in the radial direction of the roll than the Width of said drain channel providing at least one flexible projecting land between each pair of said drain channels.

References Cited UNITED STATES PATENTS 3,198,694 8/1965 Justus 29-l21 FOREIGN PATENTS 1,361,432 4/1964 France 162-372 REUBEN FRIEDMAN, Primary Examiner T. A. GRANGER, Assistant Examiner US. Cl. X.R. 162--372 

